Re: [SI-LIST] : 2.5 Gbps across a backplane

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From: DORIN OPREA (dorin.oprea@alcatel.com)
Date: Tue Oct 17 2000 - 12:16:48 PDT


I want to thank everyone for this feedback.

Dorin

"Ronald E. Nikel" wrote:

> Well that is only partially true. Equalization can be done anywhere
> using silicon, discrete filters or the interconnect
> itself.Equalization can be done :1) on silicon using discrete filter
> components2) on silicon using active devices3) on the PCB using
> discrete or active components - see HIPPI-64004) in the interconnect
> using proprietary interconnect - See Gore Cable InterconnectMy
> personal favorite approach is to use active equalization in silicon
> and working with interconnect folks to reduce loss of interconnect to
> a known band of loss for length ranges, the rest is done in
> firmware.Ron.
>
> -----Original Message-----
> From: owner-si-list@silab.eng.sun.com
> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Larry
> Miller
> Sent: Tuesday, October 17, 2000 6:44 AM
> To: renikel@ix.netcom.com
> Subject: RE: [SI-LIST] : 2.5 Gbps across a backplane
>
> It is done inside ASICs. At the frequencies of interest
> discrete parts would be problematic; digital FIR filter
> techniques are needed for picosecond pole and zero time
> constants.
>
> Broadcom makes one of the most widely available
> adaptively-equalized serial backplane drivers for general
> use. I'm sure there are others.
>
> This is getting to be a Big Deal with increasing speeds in
> networking gear.
>
> In the context of Fibre Channel and 10 Gigabit Ethernet
> transceivers the equalizers are done in the interface ICs.
> Some of these may actually be mounted inside the optical
> transceivers.
>
> Larry Miller
>
> -----Original Message-----
> From: DORIN OPREA [SMTP:dorin.oprea@alcatel.com]
> Sent: Tuesday, October 17, 2000 5:52 AM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : 2.5 Gbps across a
> backplane
>
> Hi,
>
> Can somebody describe in detail the way the
> equalization is done ?
> Are the equalizors ICs or filters ? What is the name
> of the device ?
>
> Thanks,
> Dorin
>
>
> "Dr. Edward P. Sayre" wrote:
>
> > Folks:
> >
> > A subtle issue came up in the recent T11 (Fibre
> Channel) meetings. How do
> > you spec an interconnect when adaptive equalization
> parts will be used to
> > dig out the signal? If you have really good
> eye-diagrams response then do
> > you need equalization? Conversely, if you need
> equalization because of
> > excessive deterministic jitter (read that
> insufficient rise time bandwidth)
> > or eye closure (read that too much attenuation) or
> both, then what
> > constitutes an acceptable way to specify the
> interconnect, be it backplane,
> > cable or connector?
> >
> > Now, the question of cross talk corruption of the
> signals is another
> > matter, especially when equalization is involved.
> Cross talk can be of no
> > consequence or it can be of terrible consequence,
> especially if there is a
> > requirement for byte (a 4 bit nibble) aligned serial
> data streams. Our
> > work indicates that connector cross talk in
> differential connectors appears
> > to be essentially dV/dt noise due to any asymmetries
> in the geometry of the
> > connector or interconnect (vias count here!).
> Although small, and
> > generally in the (1 - 4%) range, it is obviously a
> problem when many lines
> > are switching and especially if the time alignment is
> not within a small %
> > of the rise time between individual differential
> components. If the signal
> > is broken into its even (common mode) and odd
> (differential) mode
> > components, it can be shown that very soon the common
> mode cross talk
> > dominates the cross talk.
> >
> > So, when is cross talk an equalization issue from a
> differential eye
> > diagram point of view; and can equalization help from
> an EMI point of view?
> > I look forward to folks' ideas on this matter.
> >
> > ed sayre
> >
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> > | NORTH EAST SYSTEMS ASSOCIATES, INC. |
> > | ------------------------------------- |
> > | "High Performance Engineering & Design" |
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> > | Dr. Ed Sayre e-mail: esayre@nesa.com |
> > | NESA, Inc. http://www.nesa.com/ |
> > | 636 Great Road Tel +1.978.897-8787 |
> > | Stow, MA 01775 USA Fax +1.978.897-5359 |
> > +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~+
> >
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